HTML5

Here are a bunch of resources related to HTML5:

To run the very latest stuff (like WebGL 3D animations), you'd want to get a developer version of a browser such as Firefox or Chromium (but the latest regular releases of Firefox and Chrome run basic HTML5 stuff just fine)
http://learningwebgl.com/blog/?p=11

book in progress
http://diveintohtml5.org/

presentation
http://apirocks.com/html5/html5.html#slide1

demos
http://www.hongkiat.com/blog/48-excellent-html5-demos/
http://www.canvasdemos.com/top-100/

tutorials
http://www.webhostingsecretrevealed.com/featured-articles/learn-html5-10-must-read-lessons/
http://blog.templatemonster.com/2010/06/16/25-html5-tutorials-techniques/
http://learningwebgl.com/blog/
https://developer.mozilla.org/en/Canvas_tutorial

browser-based development environments, processing
http://edtechdev.wordpress.com/2010/03/19/browser-based-ides/
http://processingjs.org/
http://hascanvas.com/
http://energize.cc/app/
http://scenejs.org/load-ide.html

And here's a blog post about java, flash, html5:
http://edtechdev.wordpress.com/2010/02/07/whats-the-platform-of-the-future-for-developing-interactive-graphical-educational-software/